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Numerical control system

a control system and numerical control technology, applied in the direction of program control, electric programme control, instruments, etc., can solve the problems of tool wear, vibration, tool deflection, etc., and achieve the effect of reducing the number of control systems

Active Publication Date: 2020-07-16
MITSUBISHI ELECTRIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent allows a machine tool to detect different types of machining defects and determine the cause of each one. This helps to quickly fix the problem and improve the efficiency of the machine tool.

Problems solved by technology

In the cutting machining, various kinds of machining defects may occur.
The causes of machining defects include, for example, chatter vibrations, tool deflections, tool wear, and friction in feed drive mechanism.
Both chatter vibration types decrease machining accuracy and tool life.
The tool deflections are phenomena that, while the tool edge is cutting a workpiece, the tool receives cutting forces to bend from its non-cutting state, lowering the machining accuracy.
The tool wear is a phenomenon that a cutting edge of the tool repeatedly collides the workpiece to be damaged.
Thus, the tool wear lowers the quality of the machined surface and requires an increase of the cutting force.
When the characteristics of the friction in feed drive mechanism change due to movements or aging of the feed drive system, this produces a phenomenon that the relative position between the tool and the workpiece deviates from the commanded position.
Each of the phenomena mentioned above is known as a cause of a machining defect which hinders the productivity by the machine tool.

Method used

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Examples

Experimental program
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Effect test

embodiment 1

[0035]In the description of the present invention, causes of machining defects detected are called as machining defect causes. To be concrete, the machining defect causes include chatter vibrations, tool deflections, tool wear, and friction in feed drive mechanism, which will be described below.

[0036]The chatter vibrations here are vibrations which occur during cutting machining. The chatter vibrations may lower the machining accuracy and harm the life span of the tool. The chatter vibration is classified into self-excited chatter vibrations and forced chatter vibrations. The self-excited chatter vibrations are exponentially amplified by a cutting process itself. The forced chatter vibrations are generated by vibrating the machine structure with the cutting force.

[0037]The tool deflections are phenomena in which the tool edge is bent by receiving a cutting force, lowering the machining accuracy.

[0038]The tool wear is a phenomenon that the cutting edge of the tool repeatedly touches ...

embodiment 2

[0144]In Embodiment 1, it has been described that after choosing a machining defect cause, the correction amount is calculated by multiplying the control amount corresponding to the machining defect cause by a coefficient. In the present embodiment 2, description will be made about a configuration in which the correction-amount calculation unit switches rules for changing the control according to the determination results on a machining defect cause.

[0145]FIG. 7 is a block diagram of a numerical control system according to Embodiment 2 of the present invention. Note that, in FIG. 7, components identical or equivalent to those of Embodiment 1 shown in FIG. 1 are given the same symbols. Here, description will be made focusing on parts characterizing the present embodiment 2.

[0146]In the same way as the countermeasure determination unit 7 according to Embodiment 1 does, a countermeasure determination unit 7a receives the feed drive mechanism state, the dynamic characteristics informati...

embodiment 3

[0165]In the description of Embodiment 1 and 2, a machining defect cause is determined on the basis of deviation degrees. In the present embodiment 3, description will be made about a configuration in which selection of a machining defect cause is corrected on the basis of the worker's input in addition to deviation degrees.

[0166]FIG. 10 is a block diagram of a numerical control system 2b according to Embodiment 3 of the present invention. Note that, in FIG. 10, components identical or equivalent to those shown in FIG. 7 of Embodiment 1 are given the same symbols. Hence, here, description will be made focusing on parts relating to the present embodiment 3.

[0167]The numerical control system 2b includes the detection unit 4, the dynamic-characteristics-information storage unit 5, the machining-process-information storage unit 6, a countermeasure determination unit 7b, the correction-amount calculation unit 8, the control unit 9 and an input unit 27. The machine tool 1 includes the sen...

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Abstract

The numerical control system includes: detecting circuitry to obtain cutting force generated in a machine tool; controlling circuitry to calculate a control amount according to a cutting condition and to control a feed drive mechanism of the machine tool; countermeasure determining circuitry to, when it is detected from the cutting force or a state of the feed drive mechanism of the machine tool that a machining defect has occurred, calculate a plurality of deviation degrees for possible causes of the machining defect, and compare the calculated deviation degrees and to thereby determine a cause of the machining defect whose occurrence has been detected; and correction-amount calculating circuitry to calculate, according to the cause of the machining defect determined by the countermeasure determining circuitry, a correction amount with respect to the control amount, and then output the correction amount to the controlling circuitry.

Description

TECHNICAL FIELD[0001]The present invention relates to a numerical control system to control a machine tool.BACKGROUND ART[0002]A machine tool is a machining device to perform removal machining by using a tool to apply force or energy to a workpiece. Especially in a cutting tool for performing removal machining, its cutting edge moving at a high speed is put into contact with the workpiece, to produce shear fractures on the workpiece surface and thereby remove unnecessary part of the workpiece.[0003]In the cutting machining, various kinds of machining defects may occur. The causes of machining defects include, for example, chatter vibrations, tool deflections, tool wear, and friction in feed drive mechanism.[0004]The chatter vibrations are classified into two types. One is self-excited chatter vibration in which vibrations generated in a machining part develop through the machine structure and its machining process. The other is forced chatter vibration in which the vibrations by int...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G05B19/404G05B19/416G05B19/4155B23Q15/12
CPCG05B19/404G05B19/4163B23Q15/12G05B19/4155G05B19/4065G05B2219/37258G05B2219/49186G05B2219/49054G05B2219/41154G05B2219/49201
Inventor TAKAHEI, KAZUKIAZUMA, TOSHIHIRO
Owner MITSUBISHI ELECTRIC CORP
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